The simulation of film grain in a video image occurs by first creating a block (i.e., a matrix array) of transformed coefficients for a set of cut frequencies fHL, fVL, fHH and fVH associated with a desired grain pattern. (The cut frequencies fHL, fVL, fHH and fVH represent cut-off frequencies, in two dimensions, of a filter that characterizes the desired film grain pattern). The block of transformed coefficients undergoes an inverse transform to yield a bit-accurate film grain sample and the bit accurate sample undergoes scaling to enable blending with a video signal to simulate film grain in the signal.
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1. A method executed by a video signal receiving device for simulating film grain, comprising the steps of: creating, at the video signal receiving device, coefficients responsive to a band pass region associated with a desired film grain pattern, each coefficient having a value at coordinates (x, y) which is a random value for so long as x and y lie in a band pass region defined by the cut frequencies f HL , f VL , f HH and f VH , which represent cut frequencies (in two dimensions) of a filter that characterizes the desired film grain pattern, but are zero otherwise; and establishing, at the video signal receiving device, an inverse transformation of the created coefficients to yield a film grain sample for blending in a video image.
A video signal receiving device simulates film grain by creating coefficients related to a specific film grain pattern. It calculates a value for each coefficient at location (x, y). If (x, y) falls within a band pass region defined by cutoff frequencies (fHL, fVL, fHH, fVH), the coefficient is assigned a random value. Otherwise, the coefficient is set to zero. This block of coefficients undergoes an inverse transformation, producing a film grain sample. This sample can then be blended with a video image to simulate the desired film grain effect.
2. The method according to claim 1 further comprising the step of setting the coefficient at (0,0) to a zero value.
The film grain simulation method from the previous description further includes setting the coefficient at coordinates (0, 0) to a zero value. This means that after calculating the random values for coefficients within the band pass region defined by the cutoff frequencies (fHL, fVL, fHH, fVH) and setting the other coefficients to zero, the specific coefficient located at (0, 0) is explicitly set to zero before performing the inverse transformation to create the film grain sample for blending into a video.
3. The method according to claim 1 wherein each of the random values obtained for so long as x and y lie in the band pass defined by a set of cut frequencies f HL , f VL , f HH and f VH follows a Gaussian random distribution.
In the film grain simulation method, each random value assigned to a coefficient within the band pass region defined by the cutoff frequencies (fHL, fVL, fHH, fVH) follows a Gaussian (normal) random distribution. Instead of simply assigning any random number, the process generates random numbers according to a Gaussian distribution, which influences the statistical properties of the resulting film grain pattern when the inverse transformation is applied and blended into the video.
4. The method according to claim 1 wherein each of the random values is obtained by accessing an entry from a pre-computed look-up table of random values.
In the film grain simulation method, the random value assigned to each coefficient within the band pass region is obtained by looking it up in a pre-computed table of random values. Instead of generating a random number on-the-fly, the method accesses a pre-existing table or array of random numbers, which can improve performance and ensure repeatability of the film grain pattern. This is done for coordinates (x, y) that lie in the band pass region defined by the cut frequencies f HL , f VL , f HH and f VH.
5. The method according to claim 1 further including the step of scaling the film grain sample.
The film grain simulation method further includes scaling the resulting film grain sample. After generating the film grain sample through inverse transformation of the coefficients (where coefficients are random values within the band pass region), the sample is scaled, likely by multiplying each pixel value by a constant factor, before being blended with the video image. This scaling allows for control over the intensity or visibility of the simulated film grain effect in the final video.
6. A method executed by a video signal receiving device for creating coefficients used to simulate a desired film grain pattern, comprising the steps of: (a) obtaining, at the video signal receiving device, a value for each coefficient at coordinates (x, y) which is a random value for so long as x and y lie in a band pass region defined by the cut frequencies f HL , f VL , f HH and f VH , which represent cut frequencies (in two dimensions) of a filter that characterizes the desired film grain pattern, but are zero otherwise; (b) setting, at the video signal receiving device, the value of the coefficient at coordinates (x, y) to the obtained value; and (c) repeating steps (a) and (b) until a value is set for every coefficient in the block.
To create coefficients used in film grain simulation, a video signal receiving device obtains a value for each coefficient at coordinates (x, y). If (x, y) lies within a band pass region defined by cutoff frequencies (fHL, fVL, fHH, fVH), a random value is assigned; otherwise, the coefficient is zero. The device sets the coefficient at (x, y) to this obtained value. This process repeats until every coefficient in the block or array has been assigned a value, creating a complete block of coefficients representing the desired film grain pattern characteristics.
7. The method according to claim 6 further comprising the step of setting coefficient at (0,0) to a zero value.
The method for creating coefficients used to simulate a desired film grain pattern from the previous description further includes setting the coefficient at coordinates (0, 0) to zero. So, after obtaining values for coefficients (random within a defined bandpass region using cutoff frequencies fHL, fVL, fHH, and fVH; zero otherwise) and setting each coefficient to that value, the coefficient at (0, 0) is explicitly set to zero before any further processing occurs.
8. The method according to claim 6 wherein each of the random values is obtained by accessing an entry from a pre-computed look-up table of random values.
In the method for creating coefficients to simulate film grain, each random value is obtained by accessing a pre-computed look-up table. Instead of generating random values dynamically, the process consults a table of pre-generated random numbers to assign values to coefficients within the band pass region defined by the cutoff frequencies (fHL, fVL, fHH, fVH). The other coefficients outside the bandpass region are set to zero.
9. The method according to claim 6 further including the step of establishing an inverse transform on the coefficients.
The method for creating coefficients used to simulate film grain from the previous description further includes performing an inverse transform on the created coefficients. This means after obtaining values for the coefficients (random in a defined bandpass region using cutoff frequencies fHL, fVL, fHH, and fVH, and zero otherwise) and setting the coefficients to those values, an inverse transform operation (e.g., inverse Fourier transform) is applied to the block of coefficients.
10. The method according to claim 9 further including the step of scaling the inverse transform of the coefficients to yield a pattern of film grain samples.
The method from the previous description of creating coefficients to simulate film grain further includes scaling the inverse transform of the coefficients. After performing the inverse transform (where coefficients are created as random in a defined bandpass region and zero otherwise), the resulting data is scaled. This scaling adjusts the intensity of the grain pattern before it’s used, creating a simulated film grain pattern.
11. The method according to claim 10 further comprising the step of initializing a database of film grain patterns using a single block of coefficients to create all possible film grain patterns.
The method for simulating film grain further initializes a database of film grain patterns using a single block of coefficients to create all possible film grain patterns. First a single block of coefficients is created (random in a bandpass region and zero otherwise), inverse transformed, and scaled. Then, this single block serves as a seed or base from which numerous other film grain patterns are derived and stored, effectively populating the database.
12. The method according to claim 10 further comprising the step of initializing a database of film grain patterns using multiple blocks of coefficients to create all possible film grain patterns.
The method for simulating film grain initializes a database of film grain patterns using multiple blocks of coefficients to create all possible film grain patterns. Several blocks of coefficients are generated (random in a bandpass region and zero otherwise), inverse transformed, and scaled. These multiple blocks, each representing a different film grain characteristic, are used to populate the database, offering more diverse and realistic simulation capabilities compared to using just a single block.
13. Apparatus for simulating film grain, comprising one of a programmed processor and logic circuit for (1) creating coefficients responsive to a band pass region associated with a desired film grain pattern, each coefficient having a value at coordinates (x, y) which is a random value for so long as x and y lie in a band pass region defined by the cut frequencies f HL , f VL , f HH , and f VH , which represent cut frequencies (in two dimensions) of a filter that characterizes the desired film grain pattern, but are zero otherwise, 2) establishing an inverse transformation for the created coefficients; and(3) scaling the inversely transformed coefficients to create a simulated pattern of film grain for blending in a video image.
An apparatus simulates film grain using a processor or logic circuit that: 1) creates coefficients related to a specific film grain pattern. Each coefficient at location (x, y) is assigned a random value if (x, y) falls within a band pass region defined by cutoff frequencies (fHL, fVL, fHH, fVH); otherwise it is zero. 2) It performs an inverse transformation on these coefficients. 3) Finally, it scales the transformed coefficients, generating a simulated film grain pattern for blending with video.
14. The apparatus according to claim 13 wherein the one of the programmed processor or logic circuit creates the coefficients by setting the block coefficient at (0,0)to a zero value.
In the film grain simulation apparatus, the processor or logic circuit creates the coefficients by specifically setting the coefficient at coordinates (0, 0) to a zero value. Besides generating the other random values for x,y inside the bandpass region and setting the other values to zero, it is specified to also set the coefficient at (0,0) to zero. The random values for coordinates x, y are only applied if x and y lie in a band pass region defined by the cut frequencies f HL , f VL , f HH , and f VH.
15. The apparatus according to claim 13 wherein the one of the programmed processor or logic circuit obtains each of the random values by accessing an entry from a pre-computed look-up table of random values.
In the film grain simulation apparatus, the processor or logic circuit obtains each random value by accessing a pre-computed look-up table of random values. Instead of generating random numbers during the coefficient creation process (for coordinates inside the bandpass), the apparatus retrieves pre-generated random values from a stored table and assigns them to the appropriate coefficients. The random values for coordinates x, y are only applied if x and y lie in a band pass region defined by the cut frequencies f HL , f VL , f HH , and f VH.
16. Apparatus for simulating film grain, comprising: means for creating coefficients responsive to a band pass region associated with a desired film grain pattern, each coefficient having a value at coordinates (x, y) which is a random value for so long as x and y lie in a band pass region defined by the cut frequencies f HL , f VL , f HH and f VH , which represent cut frequencies (in two dimensions) of a filter that characterizes the desired film grain pattern, but are zero otherwise; means for establishing an inverse transformation for the created coefficients; and means for scaling the inversely transformed coefficients to create a simulated pattern of film grain for blending in a video image.
An apparatus simulates film grain using: means for creating coefficients that are random values inside a bandpass region (defined by cutoff frequencies fHL, fVL, fHH, and fVH) and zero otherwise; means for performing an inverse transformation on the created coefficients; and means for scaling the inversely transformed coefficients to generate a simulated film grain pattern that can be blended with a video image.
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September 26, 2005
June 25, 2013
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